6061 aluminum6061 Aluminum is probably the most common heat treatable aluminum alloy. 6061 is an aluminium alloy in which magnesium and silicon are the alloying elements. It has good mechanical properties, is heat treatable and weldable. It can be produced in several heat temper grades such as 6061-O, 6061-T4, 6061-T6, 6061-T651, 6061-T42 and recommended for the manufacture of applications requiring high corrosion resistance.